This invention relates to keyboard musical instrument and, more particularly, to a keyboard musical instrument equipped with a key-touch generator for giving appropriate key-touch to the player.
The xe2x80x9ckey-touchxe2x80x9d is an important factor to players. When a pianist initiates depressing a key of an acoustic piano, the pianist feels the key heavy. The pianist soon notices the key becoming light on the way to the end position. The change of resistance is called as xe2x80x9ckey-touchxe2x80x9d. While a pianist is playing a piece of music on the acoustic piano, he or she delicately controls the force exerted on the keys for his or her artificial expression. If an acoustic piano to be played gives a key-touch different from that of the acoustic piano familiar to a player, he or she would be puzzled how to play with expression, because the key motion is unusual. Thus, the key-touch directly concerns his or her performance, and pianists desire acoustic pianos to give the same key touch as the acoustic piano familiar to them does. Nevertheless, pianists sometimes feel the acoustic pianos different from that of the acoustic piano familiar to him or her.
A piano manufacturer has his own specifications to be applied to the manufactured pianos. When the manufacturer completes products of an acoustic piano, the manufacturer inspects the products to see whether or not the products satisfy the specification. In the inspection, the manufacturer uniformly applies the standards in the specification to the products. In the inspection, the inspector checks the products for the standard key-touch, and a tuner uniformly regulates the key touch in accordance with the specifications, if necessary. Thus, the products of the acoustic piano are expected to give the standard key-touch to pianists. However, the key-touch is to be varied with time. For this reason, the pianists usually feel other pianos different in key-touch from the piano familiar to him or her.
The grand piano is a typical example of the keyboard musical instrument. FIG. 1 shows a key forming a part of the keyboard incorporated in the standard grand piano. In the following description, term xe2x80x9cfrontxe2x80x9d is indicative of a position closer to a pianist sitting in front of a piano than a position modified with xe2x80x9crearxe2x80x9d. Term xe2x80x9clongitudinalxe2x80x9d is indicative of a direction passing through a front point and a corresponding rear point, and xe2x80x9clateral directionxe2x80x9d is perpendicular to the longitudinal direction.
Reference numeral 1 designates the key. Through-holes 2 are formed in the key 1 at intervals in the longitudinal direction, and weights 3 are snugly received in the through-holes 2. The weights 3 are formed of lead. The reason why the manufacturer uses the lead weights 3 is that the lead is deformable and easy to fill the through-holes. Another reason is the large specific weight. The key 1 is put on a balance rail 4a, and a balance pin 4b is upright on the balance rail 4a. The balance pin 4b passes through the central portion of the key 1, and the key 1 is rotatable about an axis perpendicular to the balance pin 4b. A front rail 6a laterally extends under the front portion of the key 1, and a rear rail 6b also laterally extends under the rear portion of the key 1. The front rail 6a sets a limit to the rotation of the key 1 in the counter clockwise direction, and the rear rail 6b sets a limit to the rotation of the key 1 in the clockwise direction.
An action 5 is rotatably supported by a whippen rail 9, which in turn is supported by action brackets 6c. The key 1 is held in contact with the action 5 through a capstan screw 7, and a hammer 8 is engaged with the action 5. The action is broken down into a whippen assembly 11a, a repletion lever assembly 11b and a jack 11c. The whippen assembly 11a is rotatably connected at the right end thereof to a whippen flange 11d, which in turn is fixed to the whippen rail 9. The repetition lever assembly 11b is provided on the intermediate portion of the whippen assembly 11a, and a through-hole is formed in the left portion of the repetition lever assembly 11b. The jack 11c is rotatably connected to the left portion of the whippen assembly 11a, and has a leg portion, a foot portion and a toe. The leg portion projects into the through-hole, and the hammer 8 is engaged with the leg portion. On the other hand, the toe is opposed to a regulating button 11e. 
The hammer 8 is rotatably supported by a shank flange rail 6d under an associated set of strings, and the shank flange rail 6d is supported by the action brackets 6c. The hammer 8 pushes down the whippen assembly 11a due to the self-weight, and the whippen assembly 11a in turn pushes down the capstan screw 7. The force due to the total self-weight of the hammer and whippen assembly 8/11a is exerted on the rear portion of the key 1 through the capstan screw 7, and gives rise to the rotation of the key 1 in the clockwise direction. For this reason, the rear portion is in contact with the rear rail 6b, and the front portion is spaced from the front rail 6a. 
When a pianist depresses the front portion of the key 1, the force gives rise to the rotation of the key 1 in the counter clockwise direction against the total self-weight of the hammer and whippen assembly 8/11a, and the depressed key 1 actuates the action 5. In detail, the capstan screw 7 upwardly pushes the whippen assembly 11a, and gives rise to rotation of the whippen assembly 11a about the whippen flange 11d. The jack 11c is rotated together with the whippen assembly 11a, and the toe is getting closer and closer to the regulating button 11e. When the toe is brought into contact with the regulating button 11e, the jack 11c turns about the left end of the whippen assembly 11a, and escapes from the hammer 8. When the jack 11c escapes from the hammer 8, the hammer 8 starts free rotation. Although the pianist further rotates the key 1, he or she exerts the force on the front portion of the key 1 against only the self-weight of the whippen assembly 11a. The self-weight never serves as the resistance. For this reason, the pianist feels the key 1 light.
Thus, the key 1 is moved at the balance between the moment due to the self-weight of the hammer and whippen assembly 8/11a and the moment due to the force exerted on the front portion by the pianist. The larger the difference between the moments is, the heavier the pianist feels the key 1. The weights 3 partially cancel the moment due to the total self-weight of the hammer and whippen assembly 8/11a, and render the key-touch light. However, it is difficult for the user to change the original weights 3 to other weights. Thus, only the manufacturer regulates the keys 1 to the standard key-touch by using the weights 3.
The manufacturer encounters a problem in that the lead is detrimental to health and harmful to the environment. The manufacturer tries to change the lead to another kind of metal such as iron and brass. However, these kinds of metal make the regulating work and assembling work difficult. This is because of the fact that the iron and brass are less deformable rather than the lead. In order to snugly insert the iron weights into the through-holes 2, a force fitting system is required for the iron or brass weights. However, the keys 1 are liable to be broken in the force fitting, and the force fitting is undesirable for the wooden keys 1. Otherwise, the iron or brass weights are loosely inserted into the through-holes 2, and are adhered to the wooden keys 1. The wooden keys 1 are free from the breakage. However, the adhesive compound is less reliable. Moreover, the workers keep the iron or brass weights inside of the through-holes until the adhesive compound is solidified. If the worker supplies the adhesive compound too much, the adhesive compound flows out from the through-holes, and the worker needs to wipe the excess adhesive compound. Thus, the adhesive compound makes the assembling work complicated and, accordingly, is less desirable.
A solution is proposed in Japanese Patent Application laid-open No. 2000-25147. A spring is proposed in the Japanese Patent Application laid-open. The spring 10 is provided between the whippen rail 9 and the whippen assembly 11 as shown in FIG. 1. The spring 10 exerts an elastic force on the whippen assembly 11, and causes the whippen rail 9 to support part of the total self-weight of the hammer/whippen assembly 8/11. Thus, the spring 10 cancels the part of the total self-weight of the hammer/whippen assembly 8/11 exerted on the rear portion of the key 1, and makes the key-touch light. Thus, the spring 10 serves as a key-touch regulator.
However, a problem is encountered in the prior art grand piano equipped with the key-touch regulator implemented by the spring 10 in that the distance between the hammers 8 and the associated strings is fixed after the insertion of the spring 10 between the whippen rail 9 and the whippen assembly 11. In the standard grand piano, the distance between the hammers 8 and the strings is independently regulable. The distance between the hammers 8 and the associated strings has an influence on the quality of the tone. If a set of strings generates a tone different from other tones, the distance between the hammer 8 and the string may be varied. In this situation, a tuner turns the capstan button 7 so as to lift up the whippen assembly 11 or permit the whippen assembly 11 to fall. The hammer 8 follows the whippen assembly 11, and the distance is widened or narrowed. However, when the tuner turns the capstan button 7 after the insertion of the spring 10, the elastic force is varied together with the position of the whippen assembly 11, and makes the associated key 1 different in key-touch from the other keys 1. In order to keep the key-touch uniform, the tuner keeps the capstan buttons 7 at the original height. Otherwise, the tuner deforms the springs 10 so as to decrease or increase the elastic forces. Thus, the prior art key-touch regulator 10 brings another problem into the tuning work on the standard grand piano.
Another prior art key-touch regulator is disclosed in Japanese Patent No. 2938295. Pairs of permanent magnet pieces are introduced into the keyboard. The pairs of permanent magnet pieces are attached to the keys and a stationary board in such a manner that the permanent magnet pieces attached to the keys are repulsed by the permanent magnet pieces on the stationary board. The magnetic force cancels part of the total self-weight of the hammer and action, and makes the key-touch light. However, the magnetic force is rapidly reduced inversely proportional to the square of the distance between the keys and the stationary board. In other words, the amount of force canceled is varied depending upon the current key position on the trajectory thereof. If the magnetic force is weak, the cancellation is only limited in the proximity of the initial positions of the keys. On the other hand, if the permanent magnetic pieces create extremely strong magnetic field, the pianist feels the key too light. Thus, the prior art key-touch regulator implemented by the permanent magnetic pieces can not give the appropriate key-touch to the pianists.
It is therefore an important object of the present invention to provide a keyboard musical instrument, which gives predetermined key-touch to user over the full strokes of keys regardless of a tuning work.
To accomplish the object, the present invention proposes to provide a key-touch regulator between movable keys and a stationary board so as to exerts elastic force on the keys.
In accordance with one aspect of the present invention, there is provided a keyboard musical instrument comprising an array of keys selectively moved with respect to a stationary board by a human player, a driven mechanism including plural units respectively linked with the keys of the array so as to be selectively actuated by the associated keys and exerting initial loads to the keys, respectively, and a touch-regulator having plural elastic force generating units provided between the keys and the stationary board and exerting elastic forces to the keys over the full strokes of the keys so as to cancel parts of the initial loads.